#include <iostream>
#include <thread>
// 伪函数，重写了"()"操作符的类
class background_task {
    public:
    void operator() () const {
        
        std::thread::id back_id = std::this_thread::get_id();
        std::cout << "background task thread id: " << back_id << std::endl;
        std::cout << "do something" << std::endl;
        std::cout << "do something else" << std::endl;
    }
};